Purification method of lithium difluorophosphate

Abstract

The invention provides a purification method of lithium difluorophosphate. The purification method comprises the following steps: dissolving a lithium difluorophosphate coarse product in an organic solvent to obtain a coarse product solution; adding alkaline lithium salt into the coarse product solution, and filtering undissolved substances after heating to obtain a filtrate; carrying out evaporation and concentration on the obtained filtrate to remove part of the organic solvent to obtain concentrated liquor; and adding a low polarity organic solvent into the concentrated liquor for crystallization, and then filtering and drying the mixture to obtain a lithium difluorophosphate pure product. By removing acid in the lithium difluorophosphate coarse product with the alkaline lithium salt and filtering impurities, for example, lithium fluoride and excessive alkaline lithium salt, undissolved in the solvent by selecting a proper solvent and adjusting the polarity of the solvent for crystallization, lithium difluorophosphate, the purity of which reaches over 99.9% and the acidity of which is within 70 ppm to meet the using demand of a battery is obtained more simply. The yield of the purification method is over 85%, and the energy consumption is low.

Description

technical field

[0001] The invention relates to a method for purifying lithium difluorophosphate. Background technique

[0002] Lithium difluorophosphate has the characteristics of good thermal stability, hydrolysis resistance and good electrochemical stability. Adding lithium difluorophosphate to lithium-ion batteries can effectively improve the high and low temperature performance of the battery. The principle is that a layer can be formed at the electrode interface A low-resistance SEI film can suppress the decomposition of the electrode surface at the same time.

[0003] The prior art discloses lithium monofluorophosphate (Li 2 PO 3 F) or lithium difluorophosphate (LiPO 2 f 2 ) additive electrolyte, wherein the additive can react with lithium to form a protective film on the surface of the positive or negative electrode, which can effectively inhibit the decomposition caused by the contact between the electrolyte and the electrode material, thereby inhibiting self-di...